The invention concerns a retardation installation for acid-salt-separation with a container for holding the acid accepting adsorber material, in particular an adsorber resin, and exhibiting a feed for watery acid-salt-solution by way of example from an anodizing bath, a further feed for a regenerating solution to regenerate the adsorber material, in particular demineralized (DM) water, in reverse flow relative to the acid-salt-solution, as well as a drain for the treated acid-salt-solution which has passed the absorber material and with at least one pump for transporting the acid-salt-solution and/or the regenerating solution.
Such a retardation installation is by way of example known from L. Hartinger, Handbook of Waste Water and Recycling technology, Carl Hanser Publishing House, Munich/Vienna, 1991, pages 452 ff.
These types of retardation installation for the separation of acid-salt-solutions are, for example, utilized commercially in the recycling of anodizing baths. Towards this end the acid-salt-solution (as a rule a watery solution of sulphuric acid and aluminium sulphate) is pumped in the upwards stream into a container having pellets made from adsorber resin, which are capable of adsorbing, up to a certain saturation limit, the acid from the acid-salt-solution into their surfaces. The waste water which is drained out of the container from above is then largely free from the acid components.
As soon, however, as the saturation limit of the resin pellets is reached, a so-called acid breach takes place in the run-off from the container. This means that at this time acid-salt-solution from the anodizing bath emerges from the resin container which has not been deacidified or deacidified only to a marginal extent. In order to prevent such an acid breach it has only been possible to continuously measure the acid concentration of the fluid flowing out of the resin container so that the introduction of acid-salt-solution into the resin container could be stopped before a critical value were reached. This method is, however, awkward and difficult.
It is therefore usual in retardation installations to determine, prior to the begin of the normal operation that amount of volume flow of acid-salt-solution through a container having fresh active adsorber resin at which the adsorber resin is saturated with acid and beyond which an acid breach would result.
After a precise admeasuring of this empirically determined volume amount of acid-salt-solution into the freshly active adsorber resin and without further acid measurements of the waste water from the resin container, the adsorber resin is supplied with acid-salt-solution until just prior to the saturation point. Thereafter the feeding of acid-salt-solution into the resin container is stopped and, in the downstream direction, i.e. in the opposite direction to the upward-streaming acid-salt-solution in the resin container, a regenerating solution, in the case of anodizing baths, generally demineralized water or fresh water is introduced into the resin container from above. Due to the concentration gradient the regenerating solution takes in the acid stored in the adsorber resin pellets and transports it, after leaving the resin container, back into the anodizing bath. After the passing of a certain volume flow of regenerating solution through the adsorber resin, the resin is largely acid-free and newly activated.
If then additional regenerating solution were to be, without restraint, introduced in the downward stream through the resin container into the anodizing bath, the anodizing bath would at this point due to the addition of acid-weak or acid-free water be continuously diluted. Therefore, as is the case for the prevention of acid breach in the retardation installation, the volume amount of regenerating solution is measured to determine whether it has no longer removed sufficient amounts of acid from the adsorber resin. Upon reaching this second volume amount the regeneration procedure is stopped to thereby prevent an undesirable dilution of the anodizing bath.
In the upward as well as the downward streams both the empirically determined volume amounts of acid-salt-solution or regenerating solution which are introduced to the adsorber resin must each be precisely measured and maintained. Towards this end in known retardation installations admeasuring containers are usually provided for in which the corresponding fluid volumes are measured prior to transport to the resin container. These types of admeasuring containers are, however, expensive and require substantial amounts of space. Furthermore, the retardation method is thereby complicated in that the corresponding current streams are not directly fed into the resin container rather must first be measured in the admeasuring container.
A further disadvantage of the known retardation installations is that the mechanically driven positive-displacement pumps which are usually used to transport the liquid require special safety mechanisms to prevent over-heating and the generation of prohibitively high pressures in the conduit systems during malfunctions of valves. In the event of a malfunction it would otherwise be possible for the pump to overheat and to leak or, upon exceeding a maximum pressure level, to cause a conduit to rupture. Precisely due to the utilization, for example in anodizing baths, of concentrated acids it is absolutely necessary that such a spill-off of the system in the event of a malfunction be prevented.
It is therefore the purpose of the present invention to present a retardation installation of the above described kind with which on the one hand no breach measurement or monitoring of the composition of run-off regenerating solution is necessary while, on the other hand, no admeasuring container for the volume admeasurement of the fluid streams is necessary and which additionally, in the event of malfunction caused for example by the loss of compressed air, blockage of conduits due to dirt or the improper adjustment of valves, stops in a safe operative configuration so that no special safety precaution for the pump for transporting the volume flow is necessary.